A conventional fuel injection valve includes a nozzle needle that opens or closes an injection hole through which a fuel is injected into an internal combustion engine, a control room into which a high-pressure fuel is introduced to urge the nozzle needle in a valve closing direction, an orifice body having a discharge passage through which the fuel in the control room is discharged to a low pressure portion, and a valve body that opens or closes the discharge passage by contacting with or separating from a flat sheet surface formed on the orifice body.
Upon opening of the discharge passage, the high-pressure fuel in the control room is released to the low pressure portion through the discharge passage. Accordingly, a pressure in the control room decreases, and the nozzle needle is driven to move in a valve opening direction, thereby opening the injection hole (refer to JP H10-153155 A corresponding to U.S. Pat. Nos. 5,839,661, 6,027,037, for example).
Fuel containing various foreign objects, i.e. low-quality fuel is anticipated to be widely used. When a foreign object of the fuel is stuck between the valve body and the sheet surface in vicinity of a corner part (i.e. outlet edge part) in which the sheet surface intersects with the discharge passage, the corner part escapes toward the discharge passage easily, i.e. deforms easily. Accordingly, a crack is likely to be generated in the corner part. Subsequently, damage of the sheet surface may progress from the crack of the corner part by fluid abrasive action of fine foreign objects contained in the fuel discharged through the discharge passage to the low pressure portion.
As a result, even when the valve body is in contact with the sheet surface, and the discharge passage is closed, the high-pressure fuel may leak through the damaged part of the sheet surface to the low pressure portion. Hence, a fuel injection amount and a fuel leakage amount may increase.